Strength is important to cellulosic products like paper and board, and increasing the strength of such products provides several benefits. For instance, increasing the strength of paper makes it possible to increase filler loadings and reduce virgin fibre usage, thereby reducing raw material costs in paper making processes. Similarly, increasing the strength of board makes it possible to reduce the grammage while maintaining the strength properties of cellulosic products made from the board, which also leads to savings in virgin fibre usage and reduced transportation costs, thus environmental and economic benefits.
In the manufacture of paper and board, increased dry strength can be accomplished by addition to the aqueous cellulosic suspension of a natural or synthetic polymer, optionally in combination with co-additives. Examples of such dry strength polymers include starches, carboxymethyl celluloses, cationic polyamines and cationic polyacrylamides. However, it would be desirable to be able to provide paper and board with improved dry strength.
Accordingly, there is still a need of additives which impart higher strength to paper and board and provide improvements in the manufacture of paper and board. There is also a need of additives which show an improved dry strength effect and storage stability.